Acknowledgements
We are grateful for funding from the Key Deployment Program of the Chinese Academy of Sciences (KZZD-EW-TZ-16-02), the National Natural Science Foundation of China (31170483,41101241), Foundation of Excellent Young Talents in Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences (DLSYQ12003). Appreciation is extended to students and staff of NEIGAE for sample collection and processing. We also acknowledge financial support from China Scholarship Council under the MOE-AAFC PhD Research Program sponsored by Ministry of Education of the People's Republic of China and Agriculture and Agri-Food Canada.